Search

To characterize internal processes of an observer conducting perceptual tasks, we developed an observer model that combines the perceptual template model (PTM), the attention mechanisms in the PTM framework (Lu & Dosher, 1998), and uncertainty of signal detection theory (Green & Swets, 1966). The model was evaluated with a visual search experiment conducted in a range of external noise, signal contrast, and target-distractor similarity conditions. In each trial, eight Gabor patches were shown in each of two brief intervals, with one target at a different orientation from the distractors in one of the presentations. Subjects were precued to a subset of the stimuli (1, 2, 4, or 8) and asked to report (a) which interval contained the target and (b) where the target was. Individual roles of uncertainty and of attention in visual search were investigated by comparing models with and without an attention component. The results showed that decision uncertainty alone was sufficient to account for the set-size effect, even in conditions with high target-distractor similarity. Our theoretical model and empirical results provide a coherent picture regarding how visual information is selected and processed during feature search.

We introduce a new paradigm for the assessment of auditory and visual categories in 6-month-old infants using a 2-alternative anticipatory eye-movement response. Infants were trained by 2 different methods to anticipate the location of a visual reinforcer at 1 of 2 spatial locations (right or left) based on the identity of 2 cuing stimuli. After a training phase, infants were presented with a series of generalization trials in which novel (untrained) stimuli served as the cue to the anticipatory eye movement. Four experiments illustrated that infants can learn the 2-choice discriminative response during training. Infants also showed anticipatory eye movements to novel stimuli, indicating sensitivity to variations along a variety of stimulus dimensions (e.g., color, shape, orientation, spatial frequency, pitch, and duration). In addition, the paradigm can be used to assess categorization in individual infants, thereby revealing the stimulus dimensions to which infants naturally attend.

In the domain of language research, the simultaneous presentation of a visual scene and its auditory description (i.e., the visual world paradigm) has been used to reveal the timing of mental mechanisms. Here we apply this rationale to the domain of numerical cognition in order to explore the differences between fast and slow arithmetic performance, and to further study the role of spatial-numerical associations during mental arithmetic. We presented 30 healthy adults simultaneously with visual displays containing four numbers and with auditory addition and subtraction problems. Analysis of eye movements revealed that participants look spontaneously at the numbers they currently process (operands, solution). Faster performance was characterized by shorter latencies prior to fixating the relevant numbers and fewer revisits to the first operand while computing the solution. These signatures of superior task performance were more pronounced for addition and visual numbers arranged in ascending order, and for subtraction and numbers arranged in descending order (compared to the opposite pairings). Our results show that the “visual number world”-paradigm provides on-line access to the mind during mental arithmetic, is able to capture variability in arithmetic performance, and is sensitive to visual layout manipulations that are otherwise not reflected in response time measurements.

Visually perceiving a stimulus activates a pictorial representation of that item in the brain, but how pictorial is the representation of a stimulus in the absence of visual stimulation? Here I address this question with a review of the literatures on visual imagery (VI), visual working memory (VWM), and visual preparatory templates, all of which require activating visual information in the absence of sensory stimulation. These processes have historically been studied separately, but I propose that they can provide complimentary evidence for the pictorial nature of their contents. One major challenge in studying the contents of visual representations is the discrepant findings concerning the extent of overlap (both cortical and behavioral) between externally and internally sourced visual representations. I argue that these discrepancies may in large part be due to individual differences in VI vividness and precision, the specific representative abilities required to perform a task, appropriateness of visual preparatory strategies, visual cortex anatomy, and level of expertise with a particular object category. Individual differences in visual representative abilities greatly impact task performance and may influence the likelihood of experiences such as intrusive VI and hallucinations, but research still predominantly focuses on uniformities in visual experience across individuals. In this paper I review the evidence for the pictorial content of visual representations activated for VI, VWM, and preparatory templates, and highlight the importance of accounting for various individual differences in conducting research on this topic.

1.Visual acuity is one of three basic parameters that characterize a visual system. However, few comparative studies of signals, camouflage, and ecology in general have considered visual acuity. This is unfortunate, because humans have high acuity, and thus researchers may focus on visual details of animals and habitats that are not actually visible to the relevant species. 2.Here we present AcuityView, a package for use in the software R which uses Fourier methods, measures of a viewer's acuity, viewing distance, and the size of an image to modify images. 3.AcuityView renders an image in a way that preserves only the information that an animal with a given visual acuity can detect at a certain distance, thus displaying an image that shows only the visual information available to that viewer. 4Ultimately, this will allow for a more informed analysis of what aspects of an animal's visual world may be detectable, and thus relevant to their ecology. This article is protected by copyright. All rights reserved.

The maintenance of gaze fixation during visual field testing is needed to accurately measure the functionality of the optic nerve. The present study is intended to analyze the performance of gaze fixation and evaluate five gaze fixation induction methods (GFIM) including black dot (BD; conventional method), changing color dot (CCD), alphanumeric characters (AC), flashing black dot (FBD), and bulls-eye with cross hair (BECH). Recruiting 32 participants (16 in 20s and 16 in 30s), the experiment was conducted in four steps: (1) preparation, (2) exercising the visual field testing, (3) main experiment for five GFIMs, and (4) debriefing. The performance of gaze fixation was analyzed in terms of correct fixation rate (CFR), and subjective satisfaction was evaluated in terms of ease of gaze fixation (EGF), eye fatigue (EF), and overall satisfaction (OS) using a 11-point Likert bipolar scale. The CFRs of the four new GFIMs were all higher than that of BD (BD = 86.7%, CCD = 87.9%, AC = 88.8%, FBD = 91.5%, and BECH = 88.0%). However, there was no statistically significant difference among the CFR averages of the five GFIMs, but the variances of CFR of the newly proposed GFIMs were all lower than that of BD. The subjective satisfaction of BECH (EGF = 2.0, EF = -0.4, OS = 1.6) was highest. Therefore, BECH was recommended for an effective GFIM to maintain the examinee’s gaze fixation during a visual field testing in both aspects of the performance and the subjective satisfaction.

Attention and eye movements provide a window into the selective processing of visual information. Evidence suggests that selection is influenced by various factors and is not always under the strategic control of the observer. The aims of this tutorial review are to give a brief introduction to eye movements and attention and to outline the conditions that help determine control. Evidence suggests that the ability to establish control depends on the complexity of the display as well as the point in time at which selection occurs. Stimulus-driven selection is more probable in simple displays than in complex natural scenes, but it critically depends on the timing of the response: Salience determines selection only when responses are triggered quickly following display presentation, and plays no role in longer-latency responses. The time course of selection is also important for the relationship between attention and eye movements. Specifically, attention and eye movements appear to act independently when oculomotor selection is quick, whereas attentional processes are able to influence oculomotor control when saccades are triggered only later in time. This relationship may also be modulated by whether the eye movement is controlled in a voluntary or an involuntary manner. To conclude, we present evidence that shows that visual control is limited in flexibility and that the mechanisms of selection are constrained by context and time. The outcome of visual selection changes with the situational context, and knowing the constraints of control is necessary to understanding when and how visual selection is truly controlled by the observer.

There are volumes of information available to process in visual scenes. Visual spatial attention is a critically important selection mechanism that prevents these volumes from overwhelming our visual system's limited-capacity processing resources. We were interested in understanding the effect of the size of the attended area on visual perception. The prevailing model of attended-region size across cognition, perception, and neuroscience is the zoom-lens model. This model stipulates that the magnitude of perceptual processing enhancement is inversely related to the size of the attended region, such that a narrow attended-region facilitates greater perceptual enhancement than a wider region. Yet visual processing is subserved by two major visual pathways (magnocellular and parvocellular) that operate with a degree of independence in early visual processing and encode contrasting visual information. Historically, testing of the zoom-lens has used measures of spatial acuity ideally suited to parvocellular processing. This, therefore, raises questions about the generality of the zoom-lens model to different aspects of visual perception. We found that while a narrow attended-region facilitated spatial acuity and the perception of high spatial frequency targets, it had no impact on either temporal acuity or the perception of low spatial frequency targets. This pattern also held up when targets were not presented centrally. This supports the notion that visual attended-region size has dissociable effects on magnocellular versus parvocellular mediated visual processing.

We show that visual interference impairs people’s ability to make use of visual knowledge. These results provide strong evidence that making use of stored visual knowledge—long-term memory of what things look like—depends on perceptual mechanisms. In the first set of studies, we show that presenting visual noise patterns during or after hearing a verbal cue greatly reduces the effectiveness of the cue on a simple visual discrimination task. In the second experiment, participants were tasked with answering questions about visual features of familiar objects, e.g., verifying that tables have flat surfaces. Accuracy in answering visual, but not encyclopedic questions was reduced when viewing colorful noise patterns. This result is most parsimoniously explained by positing that judgments required activation of visual representations that were being interfered with when viewing irrelevant patterns. Although much of our conceptual knowledge may abstract away from perceptual details, knowledge of what things look like appears to be represented in a visual format.

Visual spatial attention is a critical process that allows for the selection and enhanced processing of relevant objects and locations. While studies have shown attentional modulations of perceived location and the representation of distance information across multiple objects, there remains disagreement regarding what influence spatial attention has on the underlying structure of visual space. The present study utilized a method of magnitude estimation in which participants must judge the location of briefly presented targets within the boundaries of their individual visual fields in the absence of any other objects or boundaries. Spatial uncertainty of target locations was used to assess perceived locations across distributed and focused attention conditions without the use of external stimuli, such as visual cues. Across two experiments we tested locations along the cardinal and 45° oblique axes. We demonstrate that focusing attention within a region of space can expand the perceived size of visual space; even in cases where doing so makes performance less accurate. Moreover, the results of the present studies show that when fixation is actively maintained, focusing attention along a visual axis leads to an asymmetrical stretching of visual space that is predominantly focused across the central half of the visual field, consistent with an expansive gradient along the focus of voluntary attention. These results demonstrate that focusing sustained attention peripherally during active fixation leads to an asymmetrical expansion of visual space within the central visual field.

Attention, the mechanism by which a subset of sensory inputs is prioritized over others, operates at multiple processing stages. Specifically, attention enhances weak sensory signal at the perceptual stage, while it serves to select appropriate responses or consolidate sensory representations into short-term memory at the central stage. This study investigated the independence and interaction between perceptual and central attention. To do so, I used a dual-task paradigm, pairing a four-alternative choice task with a visual search task. The results showed that central attention for response selection was engaged in perceptual processing for visual search when the number of search items increased, thereby increasing the demand for serial allocation of focal attention. By contrast, central attention and perceptual attention remained independent as far as the demand for serial shifting of focal attention remained constant; decreasing stimulus contrast or increasing the set size of a parallel search did not evoke the involvement of central attention in visual search. These results suggest that the nature of concurrent visual search process plays a crucial role in the functional interaction between two different types of attention.

Visual search is thought to be guided by an active visual working memory (VWM) representation of the taskrelevant features, referred to as the search template. In three experiments using a probe technique, we investigated which eye movement metrics reveal which search template is activated prior to the search, and distinguish it from future relevant or no longer relevant VWM content. Participants memorized a target color for a subsequent search task, while being instructed to keep central fixation. Before the search display appeared, we briefly presented two task-irrelevant colored probe stimuli to the left and right from fixation, one of which could match the current target template. In all three experiments, participants made both more and larger eye movements towards the probe matching the target color. The bias was predominantly expressed in microsaccades, 100-250 ms after probe onset. Experiment 2 used a retro-cue technique to show that these metrics distinguish between relevant and dropped representations. Finally, Experiment 3 used a sequential task paradigm, and showed that the same metrics also distinguish between current and prospective search templates. Taken together, we show how subtle eye movements track task-relevant representations for selective attention prior to visual search.

This paper describes the relationship between visual attention and eye blink frequency. In an experiment, we prompted the activation of a subject’s visual attention and examined the influence of visual attention (as measured using electrodermal activity (EDA), which is meaningfully correlated with visual attention) on the subject’s eye blink frequency. Experimental results show that engagement of visual attention decreased eye blink frequency and that when visual attention was not activated, eye blink frequency increased. Knowledge of this relationship provides a technique using EDA to objectively determining a subject’s visual attention status.

In this essay I survey some recent empirical findings in vision science and show how they matter for philosophical issues in the epistemology of perception. First, I draw on some data which suggest that our visual system is a bull-shitter. Typically we call someone a bull-shitter when they don't care about whether what they say is true or false, they just care about some other goal – such as winning the argument. The bull-shitter will say some true things and some false things as long as they satisfy a truth-irrelevant end. Similarly, some empirical work suggests that the visual system, for truth-irrelevant evolutionary purposes, presents us with mostly illusory experiences which, while accurately conveying to us that an object is present, inaccurately attribute some properties to an object. Like the bull-shitter, the visual system presents us with partially accurate and partially inaccurate experiences for truth-irrelevant reasons. I then discuss what we would be justified in believing on the basis of our perceptual experiences, if our visual system is a bull-shitter.

Action game playing has been associated with several improvements in visual attention tasks. However, it is not clear how such changes might influence the way we overtly select information from our visual world (i.e. eye movements). We examined whether action-video-game training changed eye movement behaviour in a series of visual search tasks including conjunctive search (relatively abstracted from natural behaviour), game-related search, and more naturalistic scene search. Forty nongamers were trained in either an action first-person shooter game or a card game (control) for 10 hours. As a further control, we recorded eye movements of 20 experienced action gamers on the same tasks. The results did not show any change in duration of fixations or saccade amplitude either from before to after the training or between all nongamers (pretraining) and experienced action gamers. However, we observed a change in search strategy, reflected by a reduction in the vertical distribution of fixations for the game-related search task in the action-game-trained group. This might suggest learning the likely distribution of targets. In other words, game training only skilled participants to search game images for targets important to the game, with no indication of transfer to the more natural scene search. Taken together, these results suggest no modification in overt allocation of attention. Either the skills that can be trained with action gaming are not powerful enough to influence information selection through eye movements, or action-game-learned skills are not used when deciding where to move the eyes.

Background: Non-problem drinkers attend automatically to alcohol-related cues compared to non-alcohol related cues on tests of inhibitory control. Moreover, attentional bias for alcohol-related cues varies between problem and non-problem drinkers. Aim: To examine attentional bias towards alcoholic and non-alcoholic appetitive cues between problem and non-problem drinkers. Method: Forty-one university students (9 male, 32 female; Mage = 21.50) completed an eye-tracking gaze contingency paradigm, measuring the number of times participants looked at peripherally and centrally located stimuli (break frequency) when instructed to maintain focus on a target object. Stimuli consisted of appetitive alcohol-related (e.g., wine), appetitive non-alcohol-related (e.g., cola) and non-appetitive (e.g., fabric softener) stimuli. Participants were split using the Alcohol Use Disorders Identification Test (AUDIT) into non-problem (M AUDIT = 3.86) and problematic drinkers (M AUDIT = 11.59). Results: Problematic drinkers had higher break frequencies towards peripheral appetitive stimuli than towards non-appetitive stimuli, while break frequency was equivalent between appetitive cues presented centrally (alcohol and non-alcohol-related). In contrast, there were no differences in break frequency across stimuli type or cue presentation location (central or peripheral) for non-problem drinkers. Conclusion: In contrast to non-problem drinkers, people displaying more problematic consumption practices may find it more difficult to inhibit eye movements towards appetitive stimuli, particularly when in peripheral vision. This may suggest that attentional biases, as measured in terms of overt eye movements, in problem drinkers may be most powerful when the alcoholic and appetitive stimuli are not directly in field of view. An uncertainty reduction process in the allocation of attention to appetitive cues may help explain the patterns of results observed. © 2018

The existence of a central fovea, the small retinal region with high analytical performance, is arguably the most prominent design feature of the primate visual system. This centralization comes along with the corresponding capability to move the eyes to reposition the fovea continuously. Past research on visual perception was mainly concerned with foveal vision while the observers kept their eyes stationary. Research on the role of eye movements in visual perception emphasized their negative aspects, for example, the active suppression of vision before and during the execution of saccades. But is the only benefit of our precise eye movement system to provide high acuity of the small foveal region, at the cost of retinal blur during their execution? In this review, I will compare human visual perception with and without saccadic and smooth pursuit eye movements to emphasize different aspects and functions of eye movements. I will show that the interaction between eye movements and visual perception is optimized for the active sampling of information across the visual field and for the calibration of different parts of the visual field. The movements of our eyes and visual information uptake are intricately intertwined. The two processes interact to enable an optimal perception of the world, one that we cannot fully grasp by doing experiments where observers are fixating a small spot on a display.

Eye movement analysis is effective for investigating visual perception and cognition. The cost of conducting eye movement studies has decreased as a result of the recent release of low-cost commercial and open-source eye trackers. However, synchronizing visual stimulus presentation with eye movement recording is still difficult, particularly if the eye tracker does not come with a practical application programming interface. This paper introduces a Matlab/Octave toolbox named Sgttoolbox, which works in conjunction with the widely used experiment control library Psychtoolbox to control a cross-platform open-source eye tracker named SimpleGazeTracker, which is an eye-tracking application of GazeParser software. Hardware and software requirements for Sgttoolbox and its main functions are described. A test of temporal accuracy showed that eye movement sampling frequency was stable when stimulus presentation and recording were performed on a single PC, although better performance was obtained when presentation and recording were performed on separate PCs. Transferring the latest eye position from SimpleGazeTracker to Psychtoolbox script takes 2 to 4 ms on average, which causes a delay in drawing multiple visual stimuli when recording and stimulus presentation were performed on a single PC. When such a transfer delay is not importnat, Sgttoolbox would be a good choice for Psychtoolbox users who wish to conduct eye-tracking studies.

Co-registration of EEG and eye movement has promise for investigating perceptual processes in free viewing conditions, provided certain methodological challenges can be addressed. Most of these arise from the self-paced character of eye movements in free viewing conditions. Successive eye movements occur within short time intervals. Their evoked activity is likely to distort the EEG signal during fixation. Due to the non-uniform distribution of fixation durations, these distortions are systematic, survive across-trials averaging, and can become a source of confounding. We illustrate this problem with effects of sequential eye movements on the evoked potentials and time-frequency components of EEG and propose a solution based on matching of eye movement characteristics between experimental conditions. The proposal leads to a discussion of which eye movement characteristics are to be matched, depending on the EEG activity of interest. We also compare segmentation of EEG into saccade-related epochs relative to saccade and fixation onsets and discuss the problem of baseline selection and its solution. Further recommendations are given for implementing EEG-eye movement co-registration in free viewing conditions. By resolving some of the methodological problems involved, we aim to facilitate the transition from the traditional stimulus-response paradigm to the study of visual perception in more naturalistic conditions. publisher: Elsevier articletitle: Combining EEG and eye movement recording in free viewing: Pitfalls and possibilities journaltitle: Brain and Cognition articlelink: http://dx.doi.org/10.1016/j.bandc.2016.06.004 content_type: article copyright: © 2016 Elsevier Inc. All rights reserved. ispartof: Brain and Cognition vol:107 pages:55-83 ispartof: location:United States status: published

In visual search, observers try to find known target objects among distractors in visual scenes where the location of the targets is uncertain. This review article discusses the attentional processes that are active during search and their neural basis. Four successive phases of visual search are described. During the initial preparatory phase, a representation of the current search goal is activated. Once visual input has arrived, information about the presence of target-matching features is accumulated in parallel across the visual field (guidance). This information is then used to allocate spatial attention to particular objects (selection), before representations of selected objects are activated in visual working memory (recognition). These four phases of attentional control in visual search are characterized both at the cognitive level and at the neural implementation level. It will become clear that search is a continuous process that unfolds in real time. Selective attention in visual search is described as the gradual emergence of spatially specific and temporally sustained biases for representations of task-relevant visual objects in cortical maps.

We investigated characteristics of spatial attentional bias in the elderly with the use of a visual statistical learning paradigm. Triplets consisting of pictures that appeared in the same consecutive order were simultaneously presented to the left (LVF) and right visual-field (RVF) across a center fixation point. In the learning phase, both younger (N = 40) and older (N = 40) adults were instructed to attend to either the LVF or RVF and to perform a 1-back task on the visual-field. The test phase was conducted immediately after the learning phase. Implicit memory for the sequential order of the triplets was tested using a speed detection task. Younger adults showed visual statistical learning for both the attended and unattended triplets. The elderly who directed attention towards the LVF showed visual statistical learning not for the attended triplets presented in the LVF, but rather the unattended triplets presented in the RVF. These findings suggest that the elderly show a stronger visuospatial attention bias to the right visual-field, with a decline in executive function compared to younger adults.

Two types of positive afterimages differing in their structural complexity—called poor and rich—were used to investigate the visual field constancy mechanisms during eye and head movements. In the case of a poor afterimage, consistent with Emmert’s law, every eye and head movement caused the afterimage to appear moving (in exactly the same way), unlike a real object, which appeared to remain stationary during those same eye and head movements (although its retinal image moved opposite to the eye movement). However, in the case of a rich afterimage, the afterimage appeared stationary during eye movements, while a small stationary test light in the real space appeared to move, violating Emmert’s law. It is suggested that, in these two cases, the different apparent transformations reflected functioning of different constancy mechanisms. Both mechanisms implement projection of retinal images upon a hypothetical constant visual screen in strict accordance with the subject’s movements but in two different ways. The experiments have indicated that, during binocular fusion, the visual afferent system is able to use information from the structural organization of the visual flow to implement the visual field stability and to calculate gaze direction independently of proprioceptive signals.

Introduction Attentional biases for alcohol related information (AB) have often been reported for heavy drinkers. These attentional biases have been found to have predictive value regarding relapse in abstaining alcoholics. Similarly impaired inhibitory processes have also been found to be associated with heavy drinkers. This paper describes a new experimental paradigm that can be utilised to investigate attentional bias towards alcohol-related visual stimuli, specifically the ability to inhibit the orientation of initial and sustained attention, towards peripherally appearing stimuli. In this way we hope to study a novel aspect of attentional biases and how they relate to substance abuse. Methods We used a novel eye-tracking task which aims to measure inhibitory processes for AB. The experiment utilised a gaze contingency paradigm to measure the compulsion to process or attend to alcohol stimuli. 86 undergraduate participants were recruited (31 males; 55 females), aged 18–49 years (m = 20.88; sd = 4.52). A ‘break frequency’ variable was computed for each participant. This was the number of times that participants tried to look at peripheral stimuli. We argue that this variable is a direct measure of how distracting peripheral stimuli were. Results It was found that reported alcohol use was associated with the eye-tracking break frequency measure of inhibitory control. Thus, heavy drinking may be associated with decreased inhibitory control and increased attentional bias. Conclusions Results suggest that attentional bias is not just a process of stimuli becoming prioritised, but also stimuli becoming compulsory to attend and process.

Visual perception and eye movements are considered to be tightly linked. Diverse fields, ranging from developmental psychology to computer science, utilize eye tracking to measure visual perception. However, this prevailing view has been challenged by recent behavioral studies. Here, we review converging evidence revealing dissociations between the contents of perceptual awareness and different types of eye movement. Such dissociations reveal situations in which eye movements are sensitive to particular visual features that fail to modulate perceptual reports. We also discuss neurophysiological, neuroimaging, and clinical studies supporting the role of subcortical pathways for visual processing without awareness. Our review links awareness to perceptual-eye movement dissociations and furthers our understanding of the brain pathways underlying vision and movement with and without awareness.

Previous research in patients with cerebellar damage suggests that the cerebellum plays a role in covert visual attention. One limitation of some of these studies is that they examined patients with heterogeneous cerebellar damage. As a result, the patterns of reported deficits have been inconsistent. In the current study, we used functional neuroimaging (fMRI) in healthy adults (N=14) to examine whether or not the cerebellum plays a role in covert visual attention. Participants performed two covert attention tasks in which they were cued exogenously (with peripheral flashes) or endogenously (using directional arrows) to attend to marked locations in the visual periphery without moving their eyes. We compared BOLD activation in these covert attention conditions to a number of control conditions including: the same attention tasks with eye movements, a target detection task with no cueing, and a self-paced button-press task. Subtracting these control conditions from the covert attention conditions allowed us to effectively remove the contribution of the cerebellum to motor output. In addition to the usual fronto-parietal networks commonly engaged by these attention tasks, lobule VI of the vermis in the cerebellum was also activated when participants performed the covert attention tasks with or without eye movements. Interestingly, this effect was larger for exogenous compared to endogenous cueing. These results, in concert with recent patient studies, provide independent yet converging evidence that the same cerebellar structures that are involved in eye movements are also involved in visuospatial attention.

This empirical study examined whether the visual complexities of the first and second characters in two-character words play similar roles in modulating the fixation time and saccade target selection during un-spaced Chinese reading. Consistent with prior research, words with low-complexity characters were fixated for shorter times than words with high-complexity characters. Critically, saccade target selection was primarily influenced by the visual complexity of the first character of a two-character word: words with low-complexity first characters were skipped more frequently, and fixation was localized nearer to the center of the word compared with the words with high-complexity first characters. These results are important for understanding the mechanisms of eye movement control in Chinese reading and thus provide benchmark data to test models of eye movement control in Chinese reading.

We address the question of inferring the search target from fixation behavior in visual search. Such inference is possible since during search, our attention and gaze are guided toward visual features similar to those in the search target. We strive to answer two fundamental questions: what are the most powerful algorithmic principles for this task, and how does their performance depend on the amount of available eye movement data and the complexity of the target objects? In the first two experiments, we choose a random-dot search paradigm to eliminate contextual influences on search. We present an algorithm that correctly infers the target pattern up to 50 times as often as a previously employed method and promises sufficient power and robustness for interface control. Moreover, the current data suggest a principal limitation of target inference that is crucial for interface design: if the target pattern exceeds a certain spatial complexity level, only a subpattern tends to guide the observers' eye movements, which drastically impairs target inference. In the third experiment, we show that it is possible to predict search targets in natural scenes using pattern classifiers and classic computer vision features significantly above chance. The availability of compelling inferential algorithms could initiate a new generation of smart, gaze-controlled interfaces and wearable visual technologies that deduce from their users' eye movements the visual information for which they are looking. In a broader perspective, our study shows directions for efficient intent decoding from eye movements. HighlightsProviding a unified theoretical framework for intent decoding using eye movements.Proposing two new algorithms for search target inference from fixations.Studying the impact of target complexity in search performance and target inference.Sharing a large collection of code and data to promote future research in this area.

Emotionally expressive eye movement is important for facial animation. However, relation between eye movement and emotions has not been well studied. This paper integrates various sources of information to create an expressive eye model capable of expressing different emotions through vivid eye movements. First, based on statistical data and experimental studies, we endow eye model with detailed motion parameters and functions, with which detailed eye movement under neutral emotion state can be displayed. Second, an eye tracking experiment is performed to find the impact of emotional change on eye movements, and then the analysis result of tracking data are used to model eye movements under different emotion conditions. Experiment demonstrates that our eye model can reflect emotional changes of virtual character through different eye movement patterns.

The visual analysis of eye movement data is a challenging task since the data has an inherent spatio-temporal nature and is typically recorded by measuring the eye movements of various study participants and sometimes, over long time periods. Finding similar strategies among the participants while applying a visual scanning strategy is one of the most important but also most difficult tasks. In this paper we describe the eye movement plots with which we are able to visually encode the eye movement fixation sequences of several study participants as a stacked line-based representation. The two-dimensional fixation points are mapped to a time-dependent sequence of lines while edge splatting is applied to visually augment the otherwise cluttered diagrams. With this visualization concept, time-varying eye movement patterns become visible, comparable, and generate an overview representation for a set of eye movements allowing comparison tasks. We illustrate the usefulness of the technique by means of applying it to formerly recorded eye tracking data by investigating route finding tasks in public transport systems. Moreover, we describe challenges, limitations, and scalability issues of the approach.

When acting in a complex visual environment, it is essential to be able to flexibly allocate attention to parts of the visual scene that may contain goal-relevant information. The paper by Jia et al. provides novel evidence that our brains sequentially sample different objects in a visual scene. The results were obtained using "temporal response functions," in which unique electroencephalographic (EEG) signals corresponding to the processing of 2 continuously presented objects were isolated in an object-specific way. These response functions were dominated by 10-Hz alpha-band activity. Crucially, the different objects were sequentially sampled at a rate of about 2 Hz. These findings provide important neurophysiological insights into how our visual system operates in complex environments.

Prior research suggests that spontaneous saccades localized towards blank regions of space during memory storage and recall improve memory for items at the saccade locations. In the present study, we examined whether a recognition advantage can be observed when a single, exogenously directed saccade occurs during memory maintenance. We manipulated whether participants made a saccade to an item’s previous location or maintained fixation, as well as whether tested items reappeared in their original location or not. The results of three experiments showed that visual recognition was better after a saccade to the location of a probed object than after no saccade or after a saccade to the location of a non-probed object, so long as saccades went to the to-be-tested location more often than chance. Taken together, our findings demonstrate that eye movements can elicit an item-specific recognition advantage in visual working memory.

In the 10 years prior to publication the quantity of research on eye movements as they pertain to psychological processes had been increasing at a rapid rate. Originally published in 1976, the editors’ purpose was to bring together investigators representing different theoretical positions and methodological approaches to present their recent findings, to debate the theoretical points of view, and to identify and discuss the major research problems on eye movements at the time. An attempt was made to invite participants ranging all the way from promising graduate students through the established authorities in the field. The result was an intensive three-day session with meetings from early morning until late into the evening with much opportunity for formal and informal group discussion. The edited papers and transcripts of the discussions are the contents of this book.

In our natural environment, we interact with moving objects that are surrounded by richly textured, dynamic visual contexts. Yet most laboratory studies on vision and movement show visual objects in front of uniform gray backgrounds. Context effects on eye movements have been widely studied, but it is less well known how visual contexts affect hand movements. Here we ask whether eye and hand movements integrate motion signals from target and context similarly or differently, and whether context effects on eye and hand change over time. We developed a track-intercept task requiring participants to track the initial launch of a moving object (“ball”) with smooth pursuit eye movements. The ball disappeared after a brief presentation, and participants had to intercept it in a designated “hit zone.” In two experiments ( n = 18 human observers each), the ball was shown in front of a uniform or a textured background that either was stationary or moved along with the target. Eye and hand movement latencies and speeds were similarly affected by the visual context, but eye and hand interception (eye position at time of interception, and hand interception timing error) did not differ significantly between context conditions. Eye and hand interception timing errors were strongly correlated on a trial-by-trial basis across all context conditions, highlighting the close relation between these responses in manual interception tasks. Our results indicate that visual contexts similarly affect eye and hand movements but that these effects may be short-lasting, affecting movement trajectories more than movement end points. NEW & NOTEWORTHY In a novel track-intercept paradigm, human observers tracked a briefly shown object moving across a textured, dynamic context and intercepted it with their finger after it had disappeared. Context motion significantly affected eye and hand movement latency and speed, but not interception accuracy; eye and hand position at interception were correlated on a trial-by-trial basis. Visual context effects may be short-lasting, affecting movement trajectories more than movement end points.

To explore the perceptual component of chess expertise, we monitored the eye movements of expert and novice chess players during a chess-related visual search task that tested anecdotal reports that a key differentiator of chess skill is the ability to visualize the complex moves of the knight piece. Specifically, chess players viewed an array of four minimized chessboards, and they rapidly searched for the target board that allowed a knight piece to reach a target square in three moves. On each trial, there was only one target board (i.e., the "Yes" board), and for the remaining "lure" boards, the knight's path was blocked on either the first move (the "Easy No" board) or the second move (i.e., "the Difficult No" board). As evidence that chess experts can rapidly differentiate complex chess-related visual patterns, the experts (but not the novices) showed longer first-fixation durations on the "Yes" board relative to the "Difficult No" board. Moreover, as hypothesized, the task strongly differentiated chess skill: Reaction times were more than four times faster for the experts relative to novices, and reaction times were correlated with within-group measures of expertise (i.e., official chess ratings, number of hours of practice). These results indicate that a key component of chess expertise is the ability to rapidly recognize complex visual patterns.

Scene context is known to facilitate object recognition and guide visual search, but little work has focused on isolating image-based cues and evaluating their contributions to eye movement guidance and search performance. Here, we explore three types of contextual cues (a co-occurring object, the configuration of other objects, and the superordinate category of background elements) and assess their joint contributions to search performance in the framework of cue-combination and the temporal unfolding of their extraction. We also assess whether observers' ability to extract each contextual cue in the visual periphery is a bottleneck that determines the utilization and contribution of each cue to search guidance and decision accuracy. We find that during the first four fixations of a visual search task observers first utilize the configuration of objects for coarse eye movement guidance and later use co-occurring object information for finer guidance. In the absence of contextual cues, observers were suboptimally biased to report the target object as being absent. The presence of the co-occurring object was the only contextual cue that had a significant effect in reducing decision bias. The early influence of object-based cues on eye movements is corroborated by a clear demonstration of observers' ability to extract object cues up to 16° into the visual periphery. The joint contributions of the cues to decision search accuracy approximates that expected from the combination of statistically independent cues and optimal cue combination. Finally, the lack of utilization and contribution of the background-based contextual cue to search guidance cannot be explained by the availability of the contextual cue in the visual periphery; instead it is related to background cues providing the least inherent information about the precise location of the target in the scene.

Faces are salient social stimuli whose features attract a stereotypical pattern of fixations. The implications of this gaze behavior for perception and brain activity are largely unknown. Here, we characterize and quantify a retinotopic bias implied by typical gaze behavior toward faces, which leads to eyes and mouth appearing most often in the upper and lower visual field, respectively. We found that the adult human visual system is tuned to these contingencies. In two recognition experiments, recognition performance for isolated face parts was better when they were presented at typical, rather than reversed, visual field locations. The recognition cost of reversed locations was equal to ∼60% of that for whole face inversion in the same sample. Similarly, an fMRI experiment showed that patterns of activity evoked by eye and mouth stimuli in the right inferior occipital gyrus could be separated with significantly higher accuracy when these features were presented at typical, rather than reversed, visual field locations. Our findings demonstrate that human face perception is determined not only by the local position of features within a face context, but by whether features appear at the typical retinotopic location given normal gaze behavior. Such location sensitivity may reflect fine-tuning of category-specific visual processing to retinal input statistics. Our findings further suggest that retinotopic heterogeneity might play a role for face inversion effects and for the understanding of conditions affecting gaze behavior toward faces, such as autism spectrum disorders and congenital prosopagnosia.Faces attract our attention and trigger stereotypical patterns of visual fixations, concentrating on inner features, like eyes and mouth. Here we show that the visual system represents face features better when they are shown at retinal positions where they typically fall during natural vision. When facial features were shown at typical (rather than reversed) visual field locations, they were discriminated better by humans and could be decoded with higher accuracy from brain activity patterns in the right occipital face area. This suggests that brain representations of face features do not cover the visual field uniformly. It may help us understand the well-known face-inversion effect and conditions affecting gaze behavior toward faces, such as prosopagnosia and autism spectrum disorders.

During natural vision, humans make frequent eye movements but perceive a stable visual world. It is therefore likely that the human visual system contains representations of the visual world that are invariant to eye movements. Here we present an experiment designed to identify visual areas that might contain eye-movement-invariant representations. We used functional MRI to record brain activity from four human subjects who watched natural movies. In one condition subjects were required to fixate steadily, and in the other they were allowed to freely make voluntary eye movements. The movies used in each condition were identical. We reasoned that the brain activity recorded in a visual area that is invariant to eye movement should be similar under fixation and free viewing conditions. In contrast, activity in a visual area that is sensitive to eye movement should differ between fixation and free viewing. We therefore measured the similarity of brain activity across repeated presentations of the same movie within the fixation condition, and separately between the fixation and free viewing conditions. The ratio of these measures was used to determine which brain areas are most likely to contain eye movement-invariant representations. We found that voxels located in early visual areas are strongly affected by eye movements, while voxels in ventral temporal areas are only weakly affected by eye movements. These results suggest that the ventral temporal visual areas contain a stable representation of the visual world that is invariant to eye movements made during natural vision.

While whole body interaction can enrich user experience on public displays, it remains unclear how common visualizations of user representations impact users’ ability to perceive content on the display. In the work covered in this chapter, we use a head-mounted eye tracker to record visual behavior of 25 users interacting with a public display game that uses a silhouette user representation, mirroring the users’ movements. Results from visual attention analysis as well as post-hoc recall and recognition tasks on display contents reveal that visual attention is mostly on the user’s silhouette while peripheral screen elements remain largely unattended. In our experiment, content attached to the user representation attracted significantly more attention than other screen contents, while content placed at the top and bottom of the screen attracted significantly less. Screen contents attached to the user representation were also significantly better remembered than those at the top and bottom of the screen. Our findings provide fundamental insights into visual attention on interactive displays, that help designers to improve the placement of content and messages on the screen.

Eye movements in hemianopia can serve as an index of perceptual changes, residual visual function, or adaptive changes to altered vision. Central fixations are shifted towards the blind hemifield and saccades into the seeing hemifield are prolonged and less reliable. Targets in the blind hemifield are initially found with an inefficient series of small saccades, but some patients develop a compensatory search hypermetria. Blindsight studies have reported on the accuracy and reliability of saccades or pursuit responses to targets in the blind hemifield, with variable results. How hemianopic subjects scan visual information has been studied with search displays, line bisection and reading. The efficiency of scanning by hemianopic subjects is an important determinant of success in daily life activities such as driving.

Various paradigms can make visual stimuli disappear from awareness, but they often involve stimuli that are either relatively weak, competing with other salient inputs, and/or presented for a prolonged period of time. Here we explore a phenomenon that involves controlled perceptual disappearance of a peripheral visual stimulus without these limitations. It occurs when one eye's stimulus is abruptly removed during a binocular rivalry situation. This manipulation renders the remaining stimulus, which is still being presented to the other eye, invisible for up to several seconds. Our results suggest that this perceptual disappearance depends on a visual offset-transient that promotes dominance of the eye in which it occurs regardless of whether the eye is dominant or suppressed at the moment of the transient event. Using computational modeling, we demonstrate that standard rivalry mechanisms of interocular inhibition can indeed be complemented by a hypothesized transient-driven gating mechanism to explain the phenomenon. In essence, such a system suggests that visual awareness is dominated by the eye that receives transients and "sticks with" this eye-based dominance for some time in the absence of further transient events. We refer to this phenomenon as the "disrupted rivalry effect" and suggest that it is a potentially powerful paradigm for the study of cortical suppression mechanisms and the neural correlates of visual awareness.

Visual attention is one of the most important mechanisms deployed in the human visual system (HVS) to reduce the amount of information that our brain needs to process. An increasing amount of efforts has been dedicated to the study of visual attention, and this chapter proposes to clarify the advances achieved in computational modeling of visual attention. First the concepts of visual attention, including the links between visual salience and visual importance, are detailed. The main characteristics of the HVS involved in the process of visual perception are also explained. Next we focus on eye-tracking, because of its role in the evaluation of the performance of the models. A complete state of the art in computational modeling of visual attention is then presented. The research works that extend some visual attention models to 3D by taking into account of the impact of depth perception are finally explained and compared.